Vortex tube



Aug. 4, 1970 A. P. MERKULOV ETAL 3,522,710

VORTEX TUBE Filed March 1. 1968 FIG./

United States Patent Office VORTEX TUBE Alexandr Petrovich Merkulov, Ulitsa Fizkulturnaya 98a, kv. 24, and Nat-an Dmitrievich Kolyshev, Ulitsa Aerodromnaya II, kv. 60, both of Kuibyshev, U.S.S.R.

Filed Mar. 1, 1968, Ser. No. 709,686

Int. Cl. F25b 9/02 U.S. Cl. 62-5 Claims ABSTRACT OF THE DISCLOSURE A hollow cylinder of a vortex tube, having central nozzles for the tangential introduction of a gas into the cylinder, is provided with slit-type straightening diffusers at its ends for producing a substantial vacuum along the ,iaxes of the cylinder to promote cooling of a body mounted thereat. The diffusers are in the form of spaced, parallel plates, entirely open at the peripheries thereof, to define a flow passageway for the gas.

This invention relates to apparatus based on the vortex effect in gas separation as to energy (Ranques effect) and, more particularly, it relates to vortex tubes.

Known are vortex tubes comprising a hollow cylinder and nozzles disposed at one of the cylinder ends for introducing the gas tangentially with respect to the inner surface of the cylinder. The cllinder end that adjoins the nozzles is closed with a flat diaphragm in which provision is made for a centrally located round orifice.

Mounted on the opposite end of the tube is a crosspiece and throttle (see, for example Characteristics and Calculation of a Vortex-Type Refrigerator, Knolodilnaya Tekhnika, 1958, No. 3).

The gas supplied via the nozzles forms within the hol low cylinder a strong vortex that travels peripherally through the cylinder cavity towards the throttling end. The vortex travel along the cylinder cavity results in the diminution of the rotational velocity of the vortex and in concomitant enhancement of the stream turbulence, thereby causing separate stream elements that have lost the tangential velocity to be displaced to the axial region of the tube.

The reduction of the rotational velocity of the vortex brings about diminution of the radial gradient and results in the emergence of an axial static pressure gradient, the latter gradient causing stream elements in the axial region to move backwards along the cylinder axis towards the diaphragm.

As the axial stream elements approach the diaphragm, they encounter a progressively more pronounced peripheral vortex that swirls the elements in question.

Due to high turbulence, the stream in the axial region tends to rotate as if it were a solid body. Energy transfer between the axial and the peripheral stream proceeds so that in the axial stream the radial distribution of static temperature strives to become adiabatic.

This type of energy transfer results in a sharp drop of the total temperature of the stream elements in the axial region which is proportional to the ratio of the pressure on the periphery to that on the axis of the vortex (active) chamber of the cylinder.

Once the overall pressure level within the vortex zone becomes adequately high, throttling causes the elements in the axial region to discharge through the diaphragm orifice in the form of a cold stream, while the stream emerging through the throttle will have a temperature higher than that of the gas fed to the nozzles.

The resultant cooling effect, which equals the difference between the temperature of the initial gas and that of the cold stream, is limited by the ratio of the pressure 3,522,710 Patented Aug. 4, 1970 of the gas fed to the nozzles to the pressure of the emergmg cold stream and is of the order of 60-80 C. in the known vortex tubes. It is to be noted that this magnitude of cooling effect is observed only in the axial region of the vortex ahead of the diaphragm, but while the cold stream is escaping through the diaphragm orifice there is admixed therewith a warm boundary layer that flows from the nozzle outlets along the inner surface of the diaphragm towards the orifice, so that the overall effect of cooling the cold stream is diminished by 10-15 C.

An object of the present invention is to eliminate the aforesaid disadvantages and to provide a vortex tube that will, despite its relatively simple design, make it possible to enhance significantly the effect of cooling the vortex elements in the axial region.

This object is accomplished, according to the invention, by the provision of gas supply nozzles disposed centrally along a hollow cylinder Whose ends are made in the form of slit-type straightening diffusers, a feature being that the cylinder accommodates a cooled body.

An experimental vortex tube, made in accordance with the present invention, wherein the diameter of the cylinder cavity equals 30 mm., the air has a temperature of 20 C. and is fed into the nozzles at a pressure of 4 atm. and the pressure at the diffuser exit equals the ambient atmospheric pressure, provides for cooling the vortex elements in the axial region close to the nozzle outlets down to a temperature of minus 130 C.

An exemplary embodiment of the vortex tube, accord ing to the present invention, is illustrated in the accompanying drawing, wherein:

FIG. 1 is a longitudinal section of the vortex tube, and

FIG. 2 is a section taken along line II--II of FIG. 1, and partly broken away.

The vortex tube is comprised of a hollow cylinder 1 (FIG. 1) with tangential nozzles 2 (FIG. 2) in the central part of the cylinder. Mounted on the cylinder ends are arrangements which straighten the gas stream, the arrangements being made in the form of slit-type diffusers 3 constituted by spaced parallel plates 7, 8 defining a flow passageway for the gas with a continuous peripheral outlet. The plates 8 are secured to plates 7 which are integral with cylinder 1 by crescent shaped connectors 9, one of which is shown in section in the part of FIG. 2 which is broken away.

I Disposed along the axis of the cylinder 1 is a body to be cooled, i.e. a cylindrical metal rod 4. In nozzles 2, the internal area can be varied by the rotation of generating bodies 5 about axes 6.

Compressed gas is introduced into the cylinder 1 via the nozzles 2 and generates a stron vortex which travels towards both ends of the cylinder. The region near the axis of the vortex tube is occupied by cooled gases of the vortex which return from the cylinder ends towards the cylinder center and are thereafter trapped and entrained by the peripheral gases of the vortex. When the peripheral gases of the vortex traverse the straightening diffusers 3, its kinetic energy of rotary motion is transformed into pressure energy with the gases of the resultant emergence of the vortex into the ambient medium at atmospheric pressure.

In the region of the axis of the vortex zone of the cylinder, the pressure diminishes and there is produced a vacuum (absolute pressure, 0.1 atm.). Due to this pressure diminution in the axial region, the ratios of the pressures at the periphery and at the axis of the vortex become high and exert a beneficial effect of cooling phenomena in the vortex gases in the axial region.

High turbulence of the vortex gases in the axial region makes for a 'vigorous heat transfer between these gases and the cylindrical metal rod 4, disposed in the axial region is cooled.

The coefiicient of heat transfer between the gases and rod 4 is as high as 500 kcal. per sq. m. per hour per degree, so that, Where cooling effects are pronounced in the vortex gases, there are set up significant heat fluxes from the rod 4 being cooled to the vortex gases, the fluxes being as high as 3x10 kcal. per sq. 111., per hour.

To vary the magnitude of the cooling phenomena in the vortex gases of the axial region, recourse is had to alternating the internal area of nozzles 2 by rotating the bodies 5 about the axes 6.

We claim:

1. A vortex tube for gas separation as to energy, which comprises a hollow cylinder with opposite ends; means in the form of slit-type straightening ditfusers, with a continuous peripheral outlet, mounted at said ends; nozzles disposed centrally along said cylinder for introducing a gas tangentially with respect to the inner surface of said cylinder; and a body to be cooled accommodated within said hollow cylinder.

2. A vortex tube as claimed in claim 1 wherein each said slit-type straightening diffuser comprises a pair of spaced plates at each end of the cylinder extending perpendicular to the axis thereof to define a flow passageway for the gas which is entirely open at the periphery thereof and constitutes said outlet.

3. A vortex tube as claimed in claim 2 wherein one of said plates is secured to said cylinder and extends radially outwards thereof, the other plate being parallel to the first said plate.

4. A vortex tube as claimed in claim 3 wherein said plates are circular and coaxial with said cylinder.

5. A vortex tube as claimed in claim 1 wherein said nozzles include generating bodies defining a flow passageway for the gas, and means pivotably supporting said bodies to enable adjustment of the size of the passageway.

References Cited UNITED STATES PATENTS 2,907,174 10/1959 Hendal 625 3,173,273 3/1965 Fulton 625 3,237,421 3/1966 Gifford 626 3,296,807 1/1967 Feketc -3 62-5 FOREIGN PATENTS 556,867 5/1957 Belgium.

WILLIAM J. WYE, Primary Examiner 

